An adult male gorilla, who had been kept alone for many years after some excessively aggressive mating encounters, was in a cage next to two newly-arrived females. Keepers and the curator, seeing signs of interest on both sides, decided to risk a potentially dangerous introduction.
Apparently the risk was well taken for the introduction went very well and the animals almost immediately began copulating. (Over the years the reported number of copulations has ranged from simply amazing all the way up to astronomical.)
At the conclusion of all of this frantic activity the male took a few steps away from the females and collapsed face down in the water trough. The startled keepers rushed into the cage, ignoring the presence of the females, and pulled his face out of the water. They were too late. He was quite dead.
A necropsy showed that the gorilla had died of a massive heart attack and had probably been dead before he hit the floor.
Several versions of this story have made the rounds over the years. This one is the most graphic. A more likely true version relates that the gorilla was simply found dead in his cage some time later. Whichever it was, it should be mentioned that at least one of the females became pregnant as a result.